With the improvement of the level of living, there are more requirements for the vehicle. Presently, some vehicles are provided with head-up displaying systems. The head-up displaying system is mounted on a dashboard of a vehicle, projects information onto a front windshield in a form of text and image using the optical reflection principle. And a height of the projection image and eyes of a driver are generally at the same level. The driver may view a virtual image reflected by the front windshield with the projection image projected by the head-up displaying system. In this way, it is easy for the driver to combine a scene outside and the information displayed by the head-up displaying system during driving. The driver may view navigation information, the speed of the vehicle and other information without bowing his/her head, such that the problem of distracting the attention from the road ahead may be avoided, thus improving the driving security.
During a research, researchers found that the driver's eyes are always focused on a certain position, which is usually within 2.5-3 meters distance in the driving process of vehicles, therefore, the existing head-up displaying system generally directly projects the image via a transmission-type displaying screen, and then a virtual image is generated within 2.5-3 meters distance from the driver after being reflected by the front windshield. By this way, the driver can watch the road information ahead, as well as the image projected by the head up displaying system. However, when the vehicle is driving faster, in order to view more road information ahead, the driver may focus on a position farther away than three meters distance, sometimes even up to 6-7 meters distance. However, the position of image projected by the existing head-up displaying system cannot be changed, if the driver wants to get the information from the head-up displaying system, the driver needs to change the sightline between the image and the road information ahead, thus causing the security risks in the driving process.